1. Field of the Invention
The present invention relate to a plug body for liquid containers such as vacuum flasks, which are capable of opening and tightly closing a liquid passage provided in the plug body itself by means of a valve control system structured in the plug body.
2. Prior Art
Plug bodies of this type are conventionally constructed so that, when an operating button is at an upper stop position, the top surface of the button is on the same level with the plug body and the liquid passage is closed, while, when the operating button is at a bottom stop position, the top surface of the operating button is lower than the top surface of the body and the liquid passage is open (Refer to Utility Model Publication (examined) No. 60-31622/1985).
However, with the above stated conventional plug bodies, when the contained liquid has been poured out, it is not easy to check the position of the operating button, since the top surface of the operating button is lower than the top surface of the plug body. This problem of a possibility of poor visual confirmation may cause a cup-formed lid provided outside of the plug body to be screwed on without the operating button having been brought back to the closed position, resulting in leakage of the liquid contents during transport of the container. This may cause burn when hot water is contained, and is very dangerous.